Kyle has a genright stretch tank, which allows about 5 inches of stretch, and in that case you must attach the shackle hanger to the frame. alot of people use the btf cross member kit, and with that kit it adds up to be about a 7 inch stretch.
Do keep in mind...Genright also makes a tank for a 7" stretch...and even a "alien tank for up to a 9" stretch. I did see a genright stretch tank on Pirate classifieds yesterday priced at 600.
Speaking from experience, XJ leafs are a decent way to go. Here are the positive and negative aspects when setup SUA as I see them:
+ Easy way to get 4-8" of stretch
+ Decent amount of flex (12-13")
+ Relatively affordable in comparison to a linked setup
+ Simplicity (If you own a welder or have a friend with one and have a brain, you can do the swap)
+ Easy way to do an axle swap in combination with a stretch
+ Ride quality
-Decrease in ground clearance
-Possibility of axle wrap
-Still a fair amount of $ when you add it all up
On the issue of axle wrap, with my stock XJ leafs (+ extra main leaf) I do get a very small amount of it. If I dump the clutch from a dead stop, or put the pedal to the floor from a dead stop, there is a noticeable amount of vibration. It isn't harsh but is enough to be noticeable. I can't speak for the durability of the factory leafs because I've only been running them for a few months. With that said, I have heard horror stories of people bending factory XJ leafs and even breaking them. According to Redsmoke, the OME XJ leafs that he runs seem to be much more durable than factory leafs. Looking back, if I could have done anything different when I did my swap, I would have skipped the trips to the junk yard and would've invested in a set of OME XJ leafs from the get go. Once you buy two sets of junkyard leafs, you could almost have bought one set of aftermarket ones. Most junk yards want far too much for rusty old leaf springs with junk bushings. So, that's what I have to say about XJ leafs.